m4v_h263: check header first before decoding a frame.

Test: fix the file in the bug
Bug: 37660827
Change-Id: I9d6919f96c0c9f29221be1e8e852ecb21062bad9
(cherry picked from commit db545366c2e893dbbe1a42d858c52067101beda6)
(cherry picked from commit 38142b60f5144f92d99463fa1d65c543382d1264)